The present invention relates to an apparatus and method for surface treatment of a substance, such as a semiconductor wafer, to be processed by the use of ozone gas and ultraviolet light or by the use of ozone gas. Particularly, the present invention is best suited for removing a patterned resist formed on the surface of the semiconductor wafer.
FIG. 1 shows a sectional view of a prior art apparatus for surface treatment. In this apparatus, a substance 1 to be treated, for example a semiconductor wafer, is placed on a stage 30; and with a 0.2 mm to 1.0 mm gap provided between a nozzle plate 5 and the substance 1 to be treated, an ozone gas is fed from a nozzle 6 into the gap, thereby ashing and removing an organic substance such as a resist from the surface of the substance being treated. An electric heater 40 is built in the stage 30. The stage 30 is heated by supplying the current to the electric heater 40, and accordingly the substance 1 to be treated on the stage 30 is heated to increase the temperature of the resist to accelerate ashing treatment. Vacuum suction of the semiconductor wafer 1 is effected by evacuating a communicating hole through a vacuum port 4. An evacuation port 8 serves to form a stream of ozone gas in a treating space where the substance 1 to be treated is present and to evacuate an unnecessary gas generated within the space. An ultraviolet light source 7 is generally an ultraviolet lamp, and is used for surface treatment in cooperation with the ozone gas. If the ultraviolet light is applied during surface treatment, the surface treatment speed will sometimes gets higher than the surface treatment using the ozone gas alone. This apparatus for surface treatment may be either provided or not provided with the ultraviolet light source 7. Even when the apparatus is provided with the ultraviolet light source 7, whether or not the light source 7 is used during the surface treatment is arbitrary.
In the surface treatment apparatus, the substance 1 to be treated is mounted on the stage 30. The entire surface of one face of the substance 1 to be treated is in contact with the surface of the stage 30. When the surface treatment is performed in this condition, a number of foreign matters are likely to attach on this one face of the substance 1 to be treated. In the case the substance 1 is a semiconductor wafer, the one face is a face on which no device is formed, that is, the reverse side of the substance 1. The foreign matters go around to the other face of the substance being treated, that is, the face on which the devices are formed in the case of the semiconductor wafer, in the subsequent process for surface treatment, often presenting an obstacle to the subsequent surface treatment. It is because that there is a more and more increasing demand for finer sizes of device and wiring patterns formed on the surface of the substance 1 with the development of higher integrated circuits for semiconductor devices, and because that, in the following surface treatment process, the presence of the foreign matters will become a cause of defects of the substance to be processed for semiconductor devices, etc. in the event that foreign matters are present on a fine pattern. The foreign matters, if metallic ones of substantially minute sizes, will enter the device region, presenting such a vital problem as the deterioration of device characteristics. This also is because the device sensitivity has increased owing to the adoption of fine devices, and accordingly entrance of slight foreign matters gives an adverse effect to the electric characteristics of the devices and so forth.